I don't know off hand about the 172, but the last ailerons I rigged were on a 182...and they both were rigged down per the mx manual.
I was re-rigging to correct for the previous work done...which had rigged them neutral, with the control yoke nearly 90 degrees to the right. The airplane couldn't turn right in flight. When I inquired with the previous individual, who had done the work, he told me it was fine, and that it just needed a little rudder input...